1. Field of the Invention
The present invention relates to a suspension apparatus, a magnetic head apparatus, a head actuator and a magnetic recording apparatus, and particularly to a suspension apparatus, a magnetic head apparatus, a head actuator and a magnetic recording apparatus that have improved impact resistance in operating state.
2. Related Background Art
FIG. 6 is a drawing schematically showing a prior art magnetic recording apparatus. As shown in FIG. 6, the magnetic recording apparatus 101 is provided with a magnetic disk 102 serving as a rotatable magnetic recording medium and an actuator 104 for moving a magnetic head, which is floating (or hovering) above the magnetic disk 102, in a radial direction of the magnetic disk 102. The magnetic recording apparatus 101 is further provided with a movable coil 105 and a magnetic circuit 106, which constitute a voice coil motor (which will be referred to as a VCM hereinafter).
In the magnetic recording apparatus 101 having the above-described structure, a servo signal (i.e. position information) that has been written in the surface of the magnetic disk in advance is read by the magnetic head 103, and the magnetic head 103 is moved relative to the surface of the magnetic disk 102 based on the read information. Specifically, electric power is supplied to a movable coil 105 provided at the opposite end of the magnetic head 103, so that a force is generated in a magnetic circuit 106 in the directions indicated by an arrow 107. Thus, the magnetic head 103 is moved to a target track (or a target position).
FIG. 7 is a drawing schematically showing how the magnetic head apparatus is disposed in relation to the magnetic disk. As shown in this drawing, a load beam 109 is provided at the intermediate portion of the magnetic head 103. One end portion of the load beam 109 is secured to a base plate 108 that makes a junction with a head arm 115 in an actuator 104. On the other end portion of the load beam 109, there is provided a slider 110 attached thereto. In addition, an elastic spring portion is provided at the boundary 111 of the load beam 109 and the base plate 108.
In the process of writing information in the magnetic disk 102 with the above-described magnetic head, the magnetic disk 102 is rotated at several thousands revolutions per minute. The writing and other processes are performed under the state in which the rotation of the magnetic disk 102 is maintained. During that, the magnetic head 103 can be maintained in a state spaced apart from the magnetic disk 102 by a predetermined minute spacing in accordance with a balance between a pressure caused by air involved in the rotation of the magnetic disk 102 and a load exerted by a spring or other element (not shown) disposed on the actuator 104. This predetermined spacing thus maintained enable stable writing of information or other processes.
The capacity and recording density of hard disk drives have been increased rapidly, and hard disk drives with areal densities of more than 40 gigabits per square inch have been recently announced. In addition, the price of the hard disk drives per unit storage capacity has been reduced rapidly. In view of such situations, applications of hard disk drives other than conventional applications such as for servers or computers are contemplated. Specifically, applications as storage devices for digital still cameras or portable terminals such as cellular phones are contemplated.
Portable terminals including portable personal computers (which are sometimes called notebook sized personal computers) are required to be compact in the size and thickness and to be impact proof. However, generally speaking, the hard disk drive is vulnerable to impacts. This is because the magnetic head must maintain, as described in the above, a minute spacing from the magnetic disk rotating at a high rate during the process of writing information on the hard disk drive. In other words, if the hard disk drive receives an impact under an operating state such as writing, there is a considerable possibility that the magnetic head would collide with the magnetic disk that is rotating at a high rate to cause so-called head-crash.
As a solution for such a problem, Japanese Patent Application No. 9-82052 discloses, for example, a structure in which a load is given to an extension formed as a part extending from a load beam so that the center of impact acceleration created in a slider due to an externally applied impact would be shifted to the rotation center of the slider. Furthermore, Japanese Patent Application Laid-Open No. 8-102159 and No. 2001-57032 disclose a structure in which a limiter for limiting swing of a slider caused by an externally applied impact is provided with respect to the direction of the swing to reduce the amplitude of the swing movement. However, these solutions are directed to reduction of the swing that would be caused under conditions of ordinary use, but they cannot cope with situations, such as dropping of the hard disk drive to the ground or floor, which should be taken into consideration in the case of portable devices.
In other words, conventional hard disk drives have been designed under a presumption that they are used in a standstill state. Therefore, under the present circumstances, no consideration is made for behaviors of a magnetic head, a suspension and other parts of a hard disk drive on the occasion of receiving a strong impact.